This invention relates generally to optical liquid crystal systems. More particularly, it relates to liquid crystal optical processing platforms having integrated subwavelength optical elements and configured for optical switching, polarization independent variable optical attenuation, wavelength selective switching, optical multiplexing, optical demultiplexing, tunable filters and flexible optical add drop multiplexer applications.
Since the advent of fiber optics, the fiber optical communication infrastructures have become more diverse and sophisticated. The fiber optic applications range from low speed, local area networks to high speed, long distance telecommunication systems. In recent years, the demands for greater bandwidth and lower network costs have resulted in the increasingly integrated optical systems that offer multiple functionality, wafer-level integration and in a standardized traditional chip package.
Optical nanostructures have been the object of scientific investigation for several years but advances in material science and imprint lithography have only recently resulted in their cost effective manufacturing and availability as packagable array components for industry. An optical nanostructure is derived with feature sizes below the wavelength of light, so each element in the array has uniform behavior over a broad wavelength, wide acceptance angles and unique optical properties by function of varying dimensions of the underlying grating features. Optical nanostructures have been designed to function as wavelength filters, polarizers, polarizing beam splitters, combiners, and waveplates. As a result of their unique optical properties, high performance and miniature form factor, optical nanostructures represent a promising new technology that will have broad ramifications to tomorrow""s array-based optical systems.
Liquid crystal technology is known to be dynamically controlled and configured to enable a range of optical switching and signal conditioning applications. Formed with opposing plates of sealed substrates, liquid crystal cells are considered a prospect technology and integration target capable of supplying the active layer to a nanostructure integrated therewith. Wang et. Al has recently demonstrated an experimental electrically tunable filter based on a waveguide resonant sub-wavelength nanostructure-grating filter incorporating a tuning mechanism in a thin liquid crystal. The device experiment was functional and exhibited performance of 30 nanometer tuning.
Given the assertion that various useful optical processing functions can be achieved at low cost by way of integrating active liquid crystal with passive integrated nanostructured gratings, the present invention addresses specific applications directed integrated structures in liquid crystal optical switching, polarization independent variable optical attenuation, wavelength selective switching, optical multiplexing, optical demultiplexing, tunable filters and flexible optical add drop multiplexers:
The present invention contains several features and embodiments that may be configured independently or in combination with other features of the present invention, depending on the application and operating configurations. The delineation of such features is not meant to limit the scope of the invention but merely to outline certain specific features as they relate to the present invention.
It is a feature of the present invention to provide an integrated liquid crystal platform configured to function as a 1xc3x972 optical switch.
It is a feature of the present invention to provide an integrated liquid crystal platform configured to function as a 2xc3x972 optical switch.
It is a feature of the present invention to provide an integrated liquid crystal platform configured to function as a polarization independent variable optical attenuator.
It is a feature of the present invention to provide an integrated liquid crystal platform configured to function as a polarization independent variable optical attenuator capable of assuming a known state upon power failure.
It is a feature of the present invention to provide an multi-pixel integrated liquid crystal platform configured to function as a wavelength selector switch.
It is a feature of the present invention to provide an integrated liquid crystal configured to function as a tunable filter.
It is a feature of the present invention to provide a novel architecture of a flexible optical add drop multiplexer (FOADM) suitable to function with a liquid crystal tunable filter.
It is a feature of the present invention to provide a liquid crystal cell with integrated grating for use in multiplexing and demultiplexing applications.
It is a feature of the present invention to provide a liquid crystal cell whose index of refraction is changed dynamically by specific actuation of stepped electrode bands.
It is a feature of the present invention to provide a liquid crystal cell whose index of refraction can be fixed by anchoring the cell with tuned periodic alignment structures.
It is a feature of the present invention to provide a liquid crystal platform configured into a multi-function variable optical attenuator capable of defaulting to a known state in the event of power loss.
It is a feature of the present invention to provide liquid crystal tunable filters, add/drop multiplexers, wavelength selectors, switches, multiplexers and demultiplexers, that may be constructed from materials substantially impervious to moisture.
It is a feature of the present invention to provide single pixel and multiple pixel liquid crystal tunable filters, add/drop multiplexers, wavelength selectors, switches, multiplexers and demultiplexers, that may be constructed from materials substantially impervious to moisture.
It is a feature of the present invention to provide liquid crystal tunable filters, add/drop multiplexers, wavelength selectors, switches, multiplexers and demultiplexers that may contain a heater and temperature sensor integrated therein as single physical element and to provide for accurate and uniform control of heating and temperature sensing.
It is a feature of the-present invention to provide a novel method of operating liquid crystal tunable filter, optical add/drop multiplexer, wavelength selector, switch, multiplexer and demultiplexer cell and pixel array across a range of temperature without the need for lookup tables otherwise used to compensate for real time temperature changes.
It is a feature of the present invention to provide a liquid crystal tunable filter, optical add/drop multiplexer, wavelength selector, switch, multiplexer and demultiplexer cells that pass the strict telecommunications guidelines as outlined in Telcordia GR1221 without the need for hermetic housing.
It is a feature of the present invention to provide optically flat liquid crystal tunable filter, optical add/drop multiplexer, wavelength selector, switch, multiplexer and demultiplexer cells not prone to warpage during fabrication process.
It is a feature of the present invention to provide optically flat liquid crystal tunable filter, optical add/drop multiplexer, wavelength selector, switch, multiplexer and demultiplexer cells not prone to warpage when exposed to various thermal and humidity atmospheres.
It is a feature of the present invention to provide liquid crystal tunable filter, optical add/drop multiplexer, wavelength selector, switch, multiplexer and demultiplexer cells whose thickness may be controlled at nanometer resolution.
The disadvantages associated with the prior art may be overcome by a liquid crystal optical processor configured in various applications, including a liquid crystal optical switch, polarization independent variable optical attenuator, wavelength selector switch, optical multiplexer and demultiplexer, tunable filter and flexible optical add drop multiplexer. The optical processor is generally configured to include a deposited metal gasket moisture barrier bonding two opposing substrates each having a spacer layer to accurately control cell gap thickness. The optical processor may be configured in one or more pixel configurations. The optical processor may include integrated subwavelength optical gratings. It may also include an integrated thermal sensor and heater deposition layer sandwiched between or deposited on at least one or both opposing substrates.
The disadvantages associated with the prior art may further be overcome with a liquid crystal optical switch, polarization independent variable optical attenuator, wavelength selector switch, optical multiplexer/demultiplexer and tunable filter cell control system utilizing a time division scheme that multiplexes temperature sensing and heating functions across an integrated active thermal element in each device, such that the cell may generally be kept at a constant temperature. In addition or in place of heating the cell, a calibration process characterizes the profile of the cell and generates a polynomial regression formula that provides the voltage drive output the platform based on the platform temperature and state of each pixel. The control system stores the state of the liquid crystal cell, the regression formula, and reads the temperature of the liquid crystal cell to compute and assert the temperature compensated voltage drive across the pixel array.